1. Field of the Invention
This invention generally relates to flexible composite materials which are extremely heat-resistant, and methods of making same, which materials have a continuous layer or coating of solid film lubricant or glass release agent which essentially comprises an organic/inorganic silicone resin having a finely-ground particulate filler therein. The layer or coating is formed by taking an organopolysiloxane resin or mixture of such resins in a solvent, and dispersing a prescribed amount of finely-ground graphite-containing material therein, the combined materials being applied to and heat cured on a woven fibrous substrate comprised of a heat-resistant material such as glass fibers, or similar high-temperature resistant substrates. The selected substrate after coating may be severed into precisely-sized and shaped contours prior to or subsequent to heat-curing the resin containing the filler material.
The composite material may be fabricated into vacuum pads, tong liners, and the like, for handling newly-formed, hot glass articles without marring their surfaces or creating objectionable emissions from the composite material due to excessive heat. The coating cures into a thermoset hardened condition fully dispersed through the fabric substrate, and is then flexed to permit the substrate to retain an appreciable degree of flexibility. Normally, the fibrous substrate, while possessing an appreciable amount of heat resistance, cannot be employed alone without a suitable heat-resistant coating for long-term, repeated handling of hot glass articles.
2. Description of the Prior Art
It has been common practice in the glass forming art to fabricate or cover conveyor belting and hot glass transfer mechanisms for transporting hot glass articles with asbestos or asbestos-containing materials such as transite to provide heat-resistant surfaces which would not mar the glass and provide long-term operating life. Also, bucket liners and sweep arm fingers have previously been fabricated with coverings of asbestos cloth for handling hot glass articles. It is desirable to eliminate the use of all asbestos in such operations.
In the production of glassware, certain handling equipment has also been coated with graphite and petroleum oil swabbing compositions to provide lubricity and heat-resistance. In the use of such coatings, when the petroleum fraction flashes off, it can detract from effective lubrication during forming and emit undesirable emissions into the atmosphere.
The use of water-based carriers instead of the petroleum oil carriers for graphite and other lubricous materials have not been entirely satisfactory, primarily due to the high heat of vaporization of water and the resulting excessive cooling of the glass-handling equipment. In addition, it is difficult to controllably wet the handling equipment surfaces with water-based materials which are applied intermittently during production of glassware.
High temperature fabrics based on inorganic fibers such as glass, silica, quartz, and ceramics, have been proposed as replacement materials for asbestos for handling hot glass articles up to 1000.degree. F. (538.degree. C.). In glass manufacturing operations, such fabrics do not normally stand up well in repeated contact with hot glass articles because of their low resistance to abrasion. In the manufacture of glass fiber, for example, chemical treatments (sizings) such as acrylic resin or starch are used to reduce abrasive contact and fiber breakage during processing. These are organic and burn off in a high temperature environment such as in handling hot glass articles resulting in surface abrasion at the product/fabric interface and also within the fabric. Fabrics based on inorganic fibers exhibit the necessary heat resistance for hot glass handling; however, such materials require a combination with high temperature solid lubricant coating technology to be functional. This has been accomplished by this invention and coated glass fabrics have been developed which exhibit an acceptable service life in handling hot glass articles such as by conveyor ware transfer mechanisms.